Abstract

A comparison has been done between the two cases when intraband effects are included and when they are excluded in the semiconductor optical amplifier model for propagating short pulses. The numerical investigation shows that the dependence of output pulse chirping and broadening on the amplifier gain, input pulse energy, and input pulsewidth becomes stronger on inclusion of intraband effects. To prove the experimental fact of pulsewidth dependency of the amplifier saturated gain for short pulses, it is compulsory to include intraband effects in the model. We prescribe here an expression for the saturation energy as a function of pulsewidth that correctly predicts the variation obtained numerically.

Figures (8)

Variation of normalized output (a) pulse shape, (b) pulse spectrum, and (c) chirp for unsaturated gains of 10, 20, and 30 dB, respectively, for the case when intraband phenomena are neglected (i.e., ϵ=0). In (d), (e), and (f), the same is shown for the case ϵ≠0. All the figures are plotted for Ein=0.1ES and τp=5ps.

(a) shows saturated gain G as a function of input energy Ein. The value of the unsaturated gain is G0=35dB. The horizontal dashed line corresponds to the 3 dB gain saturation. (b) shows the 3 dB input saturation energy Esat,3dB as a function of pulsewidth τp for both the cases ϵ≠0 and ϵ=0. The dashed curves show the fitting obtained by using Eq. (8).

(a) shows saturated gain as a function of Ein/ES. The solid curves correspond to energy gain saturation and the dashed curve corresponds to cw gain saturation. For the latter case, the abscissa represents Pin/PS. (b) shows the ratio κ as a function of unsaturated gain G0.